Some jurisdictions also set the speed limit at, e.g., the 85th percentile of drivers' speed (https://en.wikipedia.org/wiki/Speed_limit#Method) so some drivers are always going to be speeding.

(I'm one of those speeders, too; I drive with a mentality of safety > following the strict letter of the law; I'll prefer speed of traffic if that's safer than strict adherence to the limit. That said, I know not all of my peers have the same priorities on the road, too.)